[Relation between myocardial perfusion, myocardial necrosis and residual glucose metabolism as a vitality parameter in the post-ischemic myocardium following coronary reperfusion].

The assessment of myocardial viability following interventions aiming at restitution of antegrade blood flow by PTCA and thrombolysis has become one of the most important goals to judge interventional success. Conventional markers as ECG, the extent of the regional wall motion abnormality and enzymes have conceptual limitations. We had shown previously that increased residual glucose metabolism in reperfused myocardium can be assessed by F-18 2-deoxy-glucose (FDG) and positron emission tomography (PET) and will predict functional recovery in reperfused myocardium. The present study introduces a novel concept for the evaluation of myocardial viability by the application of multiple tracer techniques and investigates tracer behaviour in relation to blood flow, regional wall motion, coronary anatomy and histology. The experimental data compare segmental uptake of F-18 FDG with the current most clinically important perfusion marker Tl-201 and Tc-99m (Sn) pyrophosphate (Tc-99mPPi) as a marker of myocardial necrosis in a canine model following a 3 hour intracoronary balloon occlusion and subsequent reperfusion and therefore in a clinically attributable occlusion and reperfusion scenario. Myocardial blood flow was assessed by microspheres, regional fractional tracer retention fractions were evaluated from tissue tracer concentrations, the arterial input function and quantitative blood flow measurements. The extent of ischemic damage was evaluated by TTC post mortem staining, histology, and histochemistry. Additional studies to illucidate the mechanism of increased glucose utilization were done by analysis of other substrates as lactate. The result within the area at risk was assessed in relation to the metabolic behaviour. PET methods were validated in the same dog model as a quantitative biochemical in-vivo assay and imaging procedure and demonstrate the ability of this noninvasive techniques to measure blood flow and myocardial metabolism, especially exogenous glucose utilization. Time dependent and repetitive PET studies may indicate a delayed recovery of myocardial metabolism following an ischemic event with a pattern of a blood flow-metabolism mismatch, characteristic for persistent viability. Metabolic data by imaging correlate with reference techniques as arterio-venous sampling and post mortem histochemical staining method using TTC, PAS, and glycogen techniques. The clinical part applies the proposed tracer concept to patients with acute myocardial infarction and following reperfusion interventions as well using conventional markers and again positron markers. These studies indicate possibilities to assess myocardial viability by the same simultaneou